Many health care tests (e.g., cholesterol, glucose, etc.) require a blood sample as the source of the analyte. Typically, the blood is withdrawn via an intravenous cannula or syringe wherein a vacuum tube is used to withdrawn and store the blood. This method, however, is not well suited for all individuals, particularly infants, elderly individuals, or ill individuals who cannot afford or are physically incapable of furnishing the required amount of blood. Also, many blood tests do not require the relatively large amount of blood withdrawn via the intravenous method.
As a result, blood lancets have been developed for withdrawing capillary blood, usually from an individual's fingertip (the “finger prick” method). These devices are more cost effective and generally less traumatic to the individual in obtaining blood samples of up to about 50 microliters. Conventional lancets typically employ a needle or blade at the end of an elongated rigid member that is essentially jabbed into the fingertip by a technician. A vial or blood blotter is then used to collect the blood. However, this procedure also has drawbacks. A successful blood sample depends in large part on the skill of the technician, who must hold the individual's hand and finger steady while accurately “aiming” the lancet and reassuring the patient. The patient's anxiety level can increase rapidly with failed attempts.
Various spring loaded sampling devices have also been developed, particularly for home diagnostic test kits. Reference is made, for example, to U.S. Pat. Nos. 4,503,856; 4,517,978; and 5,487,748. Spring-loaded devices, however, may have a tendency to prematurely actuate, for example when the individual removes the safety cap. Another common failure occurs when, by reflex, the individual pulls back from the lancet just prior to the device being triggered. This results in a grazing nick to the skin, or no skin penetration at all.
With growing demand by consumers, and emphasis by healthcare institutions for individuals to participate in and manage aspects of their own health care, home diagnostic test kits have become increasingly important. The blood sampling devices used with these diagnostic test kits play a significant role in the kit's reliability, accuracy, and acceptance by the consuming public. Thus, a continuous need exists in the art for improved blood sampling devices.